The present invention relates to a flat panel radiation detector which is used for medical and industrial use and to a process for producing the same, wherein the flat panel radiation detector is composed: of a signal reading substrate on which a radiation sensitive layer that generates an electric charge with an incidence of radiation is mounted; an upper plate placed on top of the signal reading substrate facing the signal reading substrate across the radiation sensitive layer; and resin filling the space between the signal reading substrate and the upper plate.
Formerly, in the process for producing this kind of the flat panel radiation detector (also called “FPD”), resin mold, i.e., filling with a resin, has been practiced to prevent an electric discharge when a high voltage bias is applied to the radiation sensitive layer and to protect the radiation sensitive layer (for example, see Patent Reference 1). The filling is carried out into the space surrounded by a lower face of a glass plate, a spacer and the signal reading substrate/radiation sensitive layer, wherein a spacer is disposed around the signal reading substrate and a glass plate (for example, 0.5-1 mm of thickness) made from a radiation transmitting material is disposed on top of the spacer. The injection is carried out, for example, through an inlet disposed on the spacer, and the gas in the space is let out through an outlet together with the excess resin.
When the resin is injected in such a way, the pressure of the resin injection may cause an expansion of the center of the upper plate upward, and sometimes a severe deformation or damage to the upper plate may result. To avoid this happening, usually the injection is carried out after taking precautions for the upper plate expansion by placing a flat rigid glass plate, a thick metal plate, or the like.
[Patent reference 1] Japanese Laid Open Patent Publication No. 2002-311144
However, the conventional art with such a composition has following problems.
In the conventional process for the production, since almost the same volume of the resin as the volume of the space is injected, a deformation of the upper plate occurs, concaving toward the radiation sensitive layer (inside) in the area distant from the inlet or the outlet, when an epoxy resin, which has an especially high volume shrinkage, is employed. There is a problem in that in the worst case the deformation may result in damage to a part of the upper plate due to the increase in deformation of the upper plate caused by the contraction of the resin.
Further, when the injection pressure of the resin is low, the movement of the resin is reduced during contraction resulting in not enough resin being delivered to compensate the reduced volume due to curing. This leads to more contraction in the volume. Furthermore, after curing, there is residual upward stress as the upper plate attempts to restore its original, flat shape. If the adhesion between the upper plate and the resin (especially epoxy resin) is strong, this stress becomes a force that attempts to peel away the radiation sensitive layer from the signal reading substrate. Consequently, a part of the radiation sensitive layer, for example, the peripheral area where the thickness of the layer is thin, may be separated.